1. Field of the Invention
The present invention relates to system and apparatus for controlling the unwinding of coiled material in a rolling line or a process line by generating instruction signals for reducing the unwinding speed at a predetermined moment.
2. Description of the Prior Art
FIG. 1 illustrates a conventional apparatus of this type which has various defects. Namely, FIG. 1 illustrates an automatic deceleration control apparatus which generates instruction signals for automatically decelerating the unwinding machine just before the material is all unwound. In FIG. 1, a material 2 is wound in the form of a coil on a unwinding mandrel 1 which is driven by an electric motor 3. Further, a speed indicating rotator 4 of the unwinder is coupled to the motor 3 directly or via a reduction means (not shown). Reference numeral 5 denotes a bridle which is driven by an electric motor 6. To the motor 6 is coupled a speed indicating rotator 7 directly or via a reduction gear (not shown). A counter 8 is connected to output terminals of the speed indicating rotators 4 and 7. The counter 8 produces the data related to the difference .DELTA.C in circumference between the present circumferential length of the material and the circumferential length of the previous turn, as well as the data related to the length LR of the material wound on the mandrel 1 at a moment when the unwinding machine is to be decelerated. Relying upon the data .DELTA.C, LR from the counter 8, an operation circuit 9 finds a circumferential length Cs of the coil at a moment when a deceleration instruction is to be produced. A comparator circuit 10 connected to the operation circuit 9 compares the circumferential length Cs of coil from the operation circuit 9 with a circumferential length CA of coil that is being treated, and produces a suitable deceleration instruction.
Automatic deceleration control system of the conventional unwinding machine will be described below. The coil length LR of the material 2 wound on the mandrel 1 is calculated in accordance with the following equation (1) at a moment when the unwinding machine is to be decelerated, based upon a line speed V (measured value) of the material 2 to be unwound and the remaining amount of coil Ld (preset value), ##EQU1## where .alpha. denotes deceleration, and Vo denotes a line speed when the deceleration is finished.
When the line is to be stopped at this moment, the line speed Vo should be brought to zero.
Here, the circumferential length of coil of one turn is measured to find a circumferential difference .DELTA.C (which corresponds to the thickness of the material 2 multiplied by 2.pi.) from the circumferential length of the previous turn.
If a coil of n turns is wound on the mandrel 1, the length Ln of the material wound on the mandrel 1 and the circumferential length (outermost circumference) Cn of a coil of one turn can be calculated according to the following equations: EQU Cn=.pi..multidot.DM+n.multidot..DELTA.C (2) ##EQU2## where DM denotes a diameter of the mandrel.
Therefore, a minimum number of turns n which satisfies a relation, EQU LR.ltoreq.Ln (4)
is found, and is denoted as Ns. If n=Ns is inserted into the equation (2), the circumferential length Cs of coil is found at a moment when the deceleration instruction is to be produced. That is, EQU Cs=.pi..multidot.DM+Ns.multidot..DELTA.C (5)
The circumferential length Cs of the coil is compared with the circumferential length CA of the coil which is being treated. A series of these operations are carried out every time the coil is unwound by one turn. If the deceleration instruction is generated at a moment when the following relation, i.e., EQU Cs.ltoreq.CA (6)
is established, the unwinding machine can be stopped at a suitable moment.
The above-mentioned deceleration control system will be described below in detail with reference to the conventional apparatus of FIG. 1.
The counter counts pulses produced by the speed indicating rotator 7 after every predetermined period of time to find a line speed V. The counter 8 also counts the number of pulses produced for every turn of the mandrel 1 to find the circumferential length CA of the coil. Relying upon the amount Ld of the remaining coil and the line speed V, the counter 8 further calculates a coil length LR at a moment at which the deceleration should be started, in accordance with the above-mentioned equation (1), and also finds the circumferential difference .DELTA.C of the coil. Based upon the coil length LR, circumferential difference .DELTA.C, and the diameter DM of the mandrel 1, the operation circuit 9 calculates the circumferential length Cs of coil at a moment at which the deceleration instruction should be produced, in accordance with the equations (2) and (3). The comparator circuit 10 performs the comparison as given by the equation (6), and produces the deceleration instruction when the equation (6) holds true.
According to the above-mentioned conventional system, however, the deceleration timing which is determined by a small value, i.e., by the circumferential difference .DELTA.C, is subject to be greatly affected by the variance in the thickness of the material, by the slipping of the material and by the variance in the mandrel diameter.
Namely, the circumferential difference .DELTA.C is very small, as given by, EQU .DELTA.C=2.pi..multidot.h (7)
where h denotes a thickness of the material. Here, however, it is difficult to suppress the pulse increment of the speed indicating rotator 7, which measures the circumferential length CA, so that the pulse increment is sufficiently smaller than the circumferential difference .DELTA.C. Furthermore, slipping of the material turns out to be error factor in the circumferential difference .DELTA.C. Thus, the deceleration timing is seriously affected by the disturbance. This tendency appears strikingly with the decrease in the thickness h of the material.
According to the conventional system in which the circumferential lengths are compared to find the deceleration timing, furthermore, variance in the diameter DM of the mandrel directly turns out to be an error factor in the circumferential length, and deteriorates the accuracy of the automatic deceleration control system. For the same reason, furthermore, the deceleration timing can be determined only once for every turn of the mandrel 1. Therefore, an error is inevitably introduced for every turn of the mandrel 1.